With the popularization of mobile communication devices such as cellular phones, an increasing number of base stations that execute wireless communication with mobile terminals are established. The position of base stations to be established and the sizes of communication areas need to be designed to establish the base stations so that the available communication ranges and the number of established base stations are optimized. On the other hand, one wireless base station in the current situation includes a main body thereof and about four antenna units connected to the main body. As a result, an additional base station has to be established in units of one main body and four antenna units to enlarge a communication area, causing an increase in establishment cost. Particularly, a base-station main body cannot always be established easily at a position where antenna units should be established, making it difficult to optimize available communication ranges (communication areas) and the number of established base stations.
A base station network for mobile communication disclosed in Patent Document 1 is known as a prior art of a technique using an optical cable to connect base stations to each other.    Patent Document 1: Japanese Patent, Unexamined Application, Publication No. 2001-320348